Marking apparatus with detection of excessive marking pressure

Abstract

A printing apparatus employs a rotatable cam having an enclosed cam slot for controlling the rocking motion of an inking roll without the need for a cam follower spring. The apparatus also includes an articulated printing member support assembly which executes a complex curvilinear movement under the control of a fixed cam slot without the use of linear bearings. Complementary cam profiles are used on both cam surfaces in order to maintain tangency between the inking roll and printing element during inking. A yieldable connecting link is used to prevent excessive printing pressures from being applied, and a movable filler plate closes off a slot in a front cover of the printing apparatus through which a portion of the movable printing member protrudes.

What is claimed is: 
     
       1. A marking apparatus comprising: a marking member arranged for reciprocating movement into and out of contact with a surface to be marked;   a drive source for imparting reciprocating movement to said marking member, said drive source and said marking member forming part of a load path along which marking pressure is applied to said surface to be marked;   a yieldable member in said load path for preventing excessive marking pressure from being applied between said marking member and the surface to be marked, said yieldable member comprising a strip of resilient material which is adapted to flex in compression at marking pressures in excess of a desired maximum marking pressure;   a sensor for detecting a marking pressure in excess of a desired maximum marking pressure; and   a control system coupled to said sensor and said drive source for stopping the motion of said marking member when an excessive marking pressure is detected.   
     
     
       2. A marking apparatus as claimed in claim 1, wherein said yieldable member comprises a movable drive link connecting said drive source to said marking member. 
     
     
       3. A marking apparatus as claimed in claim 1, wherein said drive source comprises a rotary crank mechanism coupled to said movable drive link. 
     
     
       4. A marking apparatus as claimed in claim 1, wherein said length of resilient material comprises a strip of spring steel. 
     
     
       5. A printing apparatus as claimed in claim 1, wherein said control system further comprises a display device for displaying an indication of excessive marking pressure to an operator. 
     
     
       6. A printer as claimed in claim 1, wherein said drive source reciprocates said marking member along a path of movement which is characterized by a predetermined travel in the direction toward a surface to be printed in the absence of marking pressure in excess of a desired maximum marking pressure, and wherein said sensor is positioned to detect the reciprocation of said marking member along said path of movement and to detect a marking pressure in excess of a desired maximum marking pressure by detecting a reduced travel of said marking member along said path of movement when said marking member is brought into contact with a surface to be printed. 
     
     
       7. A printer as claimed in claim 6, wherein said sensor comprises a proximity detector mounted at a fixed position along said path of movement to intermittently detect a portion of said marking member during the interval in which the marking member moves past the sensor and is brought into contact with the surface to be printed at normal marking pressures, and wherein said control system responds to continuous detection of said portion of said marking member during said interval by stopping the motion of said marking member. 
     
     
       8. A marking apparatus comprising: a marking member for marking a surface by undergoing reciprocating movement into and out of contact therewith;   a drive source for imparting reciprocating movement to said marking member;   a sensor for detecting a marking pressure applied by the reciprocating movement of said marking member that is in excess of a desired maximum marking pressure; and   a control system coupled to said sensor and said drive source for stopping the reciprocating movement of said marking member when an excessive marking pressure is detected; and further wherein:   said sensor is arranged to detect a marking pressure in excess of a desired maximum marking pressure by detecting a reduced travel of said marking member when said marking member is brought into contact with a surface to be printed;   said sensor comprises a proximity detector mounted at a fixed position along said path of movement to intermittently detect a portion of said marking member during the interval in which the marking member moves past the sensor and is brought into contact with the surface to be printed at normal marking pressures; and   said control system responds to continuous detection of said portion of said marking member during said interval by stopping the motion of said marking member.   
     
     
       9. A marking apparatus comprising: a marking member for marking a surface by undergoing reciprocating movement into and out of contact therewith;   a drive source for imparting reciprocating movement to said marking member;   a sensor for detecting a marking pressure applied by the reciprocating movement of said marking member that is in excess of a desired maximum marking pressure;   a control unit coupled to said sensor; and   a display device coupled to said control unit for displaying an indication of excessive marking pressure to an operator.   
     
     
       10. A marking apparatus as claimed in claim 9, wherein said drive source reciprocates said marking member along a path of movement which is characterized by a predetermined travel in the direction toward a surface to be printed in the absence of marking pressure in excess of a desired maximum marking pressure, and wherein said sensor is positioned to detect the reciprocation of said marking member along said path of movement and to detect a marking pressure in excess of a desired maximum marking pressure by detecting a reduced travel of said marking member along said path of movement when said marking member is brought into contact with a surface to be printed. 
     
     
       11. A marking apparatus as claimed in claim 10, wherein said sensor comprises a proximity detector mounted at a fixed position along said path of movement to intermittently detect a portion of said marking member during the interval in which the marking member moves past the detector and is brought into contact with the surface to be printed at normal marking pressures, and wherein said control unit responds to continuous detection of said portion of said marking member during said interval by causing said display device to display an indication of excessive marking pressure. 
     
     
       12. A method for limiting the maximum marking pressure in a marking apparatus comprising a marking member arranged for reciprocating movement into and out of contact with a surface to be printed and a drive source for said marking member, said drive source and said marking member forming part of a load path along which marking pressure is applied to said surface to be printed, said method comprising the steps of interposing in said load path a resilient member having a non-linear restoring force characteristic, causing said resilient member to yield in response to a marking pressure in excess of a desired maximum marking pressure, detecting the yielding of said resilient member and stopping operation of said drive source in response to said detection. 
     
     
       13. A method for limiting the maximum marking pressure in a marking apparatus comprising a marking member arranged for reciprocating movement into and out of contact with a surface to be printed and a drive source for said marking member, said drive source and said marking member forming part of a load path along which marking pressure is applied to said surface to be printed, said method comprising the steps of interposing in said load path a resilient member having a non-linear restoring force characteristic, causing said resilient member to yield in response to a marking pressure in excess of a desired maximum marking pressure, detecting the yielding of said resilient member and displaying an indication of excessive marking pressure in response to said detection. 
     
     
       14. A method for detecting an excessive marking pressure in a marking apparatus comprising a marking member for marking a surface by undergoing reciprocating movement into and out of contact therewith during successive marking strokes and a drive source for reciprocating said marking member, said method comprising the steps of detecting a reduced travel of said marking member when said marking member is brought into contact with a surface to be marked during a marking stroke, and displaying an indication of excessive marking pressure in response to said detection. 
     
     
       15. A method as claimed in claim 14, further comprising the step of stopping the operation of said drive source in response to said detection. 
     
     
       16. A method as claimed in claim 14, wherein the step of detecting a reduced travel of said marking member comprises the step of detecting the motion of said marking member past a sensor. 
     
     
       17. A marking apparatus comprising: a marking member arranged for reciprocating movement into and out of contact with a surface to be marked;   a drive source for imparting reciprocating movement to said marking member;   a movable drive link connecting said drive source to said marking member, said movable drive link being yieldable to prevent excessive marking pressure from being applied between said marking member and the surface to be marked;   a sensor for detecting a marking pressure in excess of a desired maximum marking pressure; and   a control system coupled to said sensor and said drive source for stopping the motion of said marking member when an excessive marking pressure is detected.   
     
     
       18. A marking apparatus as claimed in claim 17, wherein said drive source comprises a rotary crank mechanism coupled to said movable drive link. 
     
     
       19. A marking apparatus as claimed in claim 17, wherein said movable drive link comprises a length of resilient material which is adapted to flex at marking pressures in excess of a desired maximum marking pressure. 
     
     
       20. A marking apparatus as claimed in claim 19, wherein said length of resilient material comprises a strip of spring steel. 
     
     
       21. A printing apparatus as claimed in claim 17, wherein said control system further comprises a display device for displaying an indication of excessive marking pressure to an operator. 
     
     
       22. A printer as claimed in claim 17, wherein said drive source reciprocates said marking member along a path of movement which is characterized by a predetermined travel in the direction toward a surface to be printed in the absence of marking pressure in excess of a desired maximum marking pressure, and wherein said sensor is positioned to detect the reciprocation of said marking member along said path of movement and to detect a marking pressure in excess of a desired maximum marking pressure by detecting a reduced travel of said marking member along said path of movement when said marking member is brought into contact with a surface to be printed. 
     
     
       23. A printer as claimed in claim 22, wherein said sensor comprises a proximity detector mounted at a fixed position along said path of movement to intermittently detect a portion of said marking member during the interval in which the marking member moves past the sensor and is brought into contact with the surface to be printed at normal marking pressures, and wherein said control system responds to continuous detection of said portion of said marking member during said interval by stopping the motion of said marking member. 
     
     
       24. A method for limiting the maximum marking pressure in a marking apparatus comprising a marking member arranged for reciprocating movement into and out of contact with a surface to be printed, a drive source for said marking member, and a movable drive link connecting said printing member to said drive source, said method comprising the steps of causing said movable drive link to yield in response to a marking pressure in excess of a desired maximum marking pressure, detecting the yielding of said movable drive link and stopping operation of said drive source in response to said detection. 
     
     
       25. A method as claimed in claim 24, further comprising the steps of detecting the yielding of said movable drive link and displaying an indication of excessive marking pressure in response to said detection. 
     
     
       26. A marking apparatus comprising: a marking member arranged for reciprocating movement into and out of contact with a surface to be marked during successive marking cycles;   a drive source coupled to said marking member for imparting reciprocating movement thereto;   a home position sensor for detecting a predetermined home position of said marking member in proximity to said surface, said home position sensor producing a first output during a marking cycle in which the marking pressure applied to said surface by said marking member is within a desired range and a second output during a marking cycle in which the marking pressure applied to said surface by said marking member is in excess of a desired maximum marking pressure; and   a control system coupled to said drive source and to said home position sensor for controlling the operation of said marking apparatus in accordance with said first and second outputs.   
     
     
       27. A marking apparatus as claimed in claim 26, wherein: said control system is responsive to a start command for initiating each successive marking cycle;   said control system is operative to stop the reciprocating movement of said marking member and to await said start command when said home position sensor produces said first output; and   said control system is operative to stop the reciprocating movement of said marking member and to ignore said start command when said home position sensor produces said second output.   
     
     
       28. A marking apparatus as claimed in claim 26, wherein said control system further comprises a display device, and further wherein: said control system is responsive to a start command for initiating each successive marking cycle;   said control system is operative to stop the reciprocating movement of said marking member and to await said start command when said home position sensor produces said first output; and   said control system is operative to stop the reciprocating movement of said marking member and to display an indication of excessive marking pressure using said display device when said home position sensor produces said second output.   
     
     
       29. A marking apparatus as claimed in claim 26, wherein said home position sensor is arranged to detect a marking pressure in excess of a desired marking pressure by detecting a reduced travel of said marking member between said home position and said surface. 
     
     
       30. A marking apparatus as claimed in claim 26, wherein said first and second outputs comprise different numbers of signal transitions produced at the output of said home position sensor, and wherein said control system includes a counter for counting said signal transitions. 
     
     
       31. A method for operating a marking apparatus comprising a marking member arranged for reciprocating movement into and out of contact with a surface to be printed during successive marking cycles, said method comprising the steps of providing a home position sensor to detect a predetermined home position of said marking member in proximity to said surface, and detecting an abnormal output of said home position sensor to provide an indication that the marking pressure applied to said surface by said marking member during a marking cycle is in excess of a desired maximum value. 
     
     
       32. A method as claimed in claim 31, further comprising the step of inhibiting further marking cycles in response to the detection of an abnormal output from said home position sensor. 
     
     
       33. A method as claimed in claim 31, further comprising the step of displaying an indication of excess marking pressure in response to the detection of an abnormal output from said home position sensor.